It was a relationship that began in political controversy but progressed to a secret family union: Tony Blair, it was revealed , is godfather to Rupert Murdoch's nine-year-old daughter, Grace, the second youngest of his six children.

In a culmination of 15 years of political intimacy, the former Labour prime minister was present at the star-studded baptism of the child on the banks of the Jordan, at the spot where Jesus is said to have undergone the same ceremony, according to an article in Vogue magazine.

With the Murdochs and their children dressed in white – and present at the invitation of Queen Rania of Jordan – the event was photographed in Hello! magazine, complete with an ethereal front cover image of a smiling Murdoch in an open-necked shirt.

But no mention was made of Blair's participation, which was revealed only in a rare interview by Murdoch's wife, Wendi Deng, in a forthcoming edition of Vogue.

Although she has traditionally kept a low profile, Deng's interview comes after she catapulted herself into the public spotlight by leaping from a chair to lash out at a foam-pie thrower who attempted to target Murdoch during his questioning before the Commons culture, media and sport committee in July.

In the Vogue article the former Labour leader, is described as "one of Murdoch's closest friends".

Murdoch's company, News Corporation, confirmed the longstanding link between the two men, although it is not known when Murdoch asked Blair to act as a godparent and how far this predated the actual baptism.

Grace was baptised a few weeks before Easter of 2010, and therefore shortly before the last general election.

When the Jordanian baptism was originally reported by Hello!, it noted that actors Nicole Kidman and Hugh Jackman, both friends of the Murdochs, were godparents to Grace and her sister Chloe.

The involvement of Blair was admitted by Deng in the interview shortly before her husband flew to London to deal with the phone-hacking crisis in the wake of revelations that the News of the World had targeted the mobile phone of murdered schoolgirl Milly Dowler.

Deng, who said she was not sleeping because of the stress of dealing with the phone-hacking affair, added in the interview: "Of course, as Rupert's wife, I think it's unfair on him to be going through this. I worry about him being alone. He has no PR people advising him. He tells me not to come but I'm flying to London for the hearing. I want to be with him."

In July it was reported that Blair rang Gordon Brown to ask him to tell his friend and ally, the Labour MP Tom Watson, to lay off attacking News Corporation over the phone-hacking issue. Brown is thought to have refused the request, although neither Blair nor Brown has confirmed such a conversation took place.

A spokesman for Blair last night declined to comment on the godfather link.

Blair's wooing of Murdoch dates to 1995, when the leader of the opposition provoked a political row by accepting an invitation to address a News Corporation conference on Hayman Island, Australia, in July of that year. Labour under Neil Kinnock had previously been demonised in Murdoch's Sun, to the point where some believed the tabloid's opposition had cost the party the 1992 election.

When Blair opted to attend, he justified the decision to his spokesman, Alastair Campbell, that "not to go was to say carry on and do your worst, and we knew their worst was very bad indeed," according to his memoirs. "It seems obvious," he added in his book, A Journey. "The country's most powerful newspaper proprietor, whose publications have hitherto been rancorous in their opposition to the Labour party, invites us into the lion's den. You go, don't you?" Blair also noted that Paul Keating, then Australia PM, felt Murdoch was "a bastard, but one you could deal with".

The would-be PM's performance at the News Corp event was seen as a clear sign that Labour was becoming electable – and marked the beginning of a long, close friendship between the two men.

Labour benefited from the loyal support of Murdoch newspapers, with the Sun switching from Conservative to Labour in the run-up to the 1997 election, and the Times dropping the Conservatives in 1997 and endorsing Labour in 2001. Meanwhile, Labour placed few restrictions on the operation of either News Corp's newspapers or BSkyB, in which News Corp owned a 39.1% stake, during its time in office.

Support from the Murdoch titles intensified at the time of the Iraq war, and Murdoch and Blair were in close contact through Blair's premiership, speaking, for example, on the phone three times in the nine days before the Iraq war. Information released by No 10 under freedom of information rules also showed the pair spoke on the day the Hutton report into the death of Dr David Kelly was published.

By the end of his premiership, Blair wrote of Murdoch in his memoirs that he "came to have a grudging respect and even a liking for him". He added: "He was hard, no doubt. He was rightwing. I did not share or like his attitudes on Europe, social policy or on issues like gay rights, but there were two points of connection: he was an outsider and he had balls."